Ataxia Telangiectasia (AT) is a rare genetic disease caused by biallelic mutations in the ataxia telangiectasia mutated (ATM) gene, most of which are truncations. The causative gene, ATM, encodes a PI3Kinase protein shown to play a pivotal role in the response to DNA damage and in cell cycle control (Kastan et al., 2000). Homozygosity or compound heterozygosity for ATM mutations results in a multi-systemic disorder, mainly involving the nervous and immune system. The major clinical feature of AT is severe progressive neurodegeneration with onset in infancy. These features include ataxia of the trunk and limbs, progressive supranuclear ophthalmoplegia, dysarthria, swallowing incoordination, facial hypomimia and delayed peripheral neuropathy. Other clinical features of patients with the classical phenotype include oculocutaneous telangiectasia, immunodeficiency with recurrent respiratory tract infections, radiosensitivity and an increased incidence of cancer. In the classic form, patients are wheel chair dependent by the age of 10 and their life expectancy is around 25 years of age (Crawford, 2000).
AT occurs in between 0.5-2.5 in 100,000 population worldwide (NIH, 1995; Anheim et al., 2012). The estimated prevalence of AT is 1 in 100000 population in the EU (Orphanet 2014), and 1-2.5 in 100,000 population in the USA (Swift et al., 1986; Chun et al. 2004). An estimated 1% of the U.S. population, or about 2.5 million people, may be carriers of AT. AT has no racial, economic, geographic or education barriers. Both males and females are equally affected. It is believed that many children with AT, particularly those who die at a young age, are never properly diagnosed. Therefore, this disease may actually be more common than projected.